This invention relates generally to dispensing devices and, particularly to repeating dispensers.
Repeating dispensers have been advantageously utilized in chromatographic work, chemical analysis or tests and the like, but it is to be understood that the utility is not confined thereto. Repeating dispensers are utilized to provide, with one filling operation that sucks in a relatively large amount of fluid, repetitive, accurate discharges of exactly the same minute quantities of fluid.
U.S. Pat. No. 3,161,323 shows a repeating dispenser of the type aforementioned, and the construction thereof is simple; however, the dispenser has an index rod having rack teeth thereon and which is exposed to the outside, thus, it is difficult to handle the dispenser.
German patent disclosure No. P 2736551 discloses a generally tubular repeating dispenser having an actuating button on the top end. The dispenser is very easy to handle; however, there is a shortcoming that the relatively large amount of the liquid sucked and stored in the dispenser can only be dispensed by repeatedly depressing the actuating button, and that it is not easy to disassemble a cylinder and a piston from the dispenser which would be required in changing the liquid being sucked in and dispensed.
German patent disclosure No. 2926691 shows another repeating dispenser generally solving the problems aforementioned; however, there are many levers projecting sidewise from a generally tubular main body thus it is objectionable in the handling operation of the piston device.
The inventor has shown in U.S. Pat. No. 4,467,942 a repeating dispenser comprising a tubular main body, an actuating member slidably disposed in the main body with the upper end thereof projecting out of the upper end of the main body and having a pressure button thereon, a spring for biasing upwards the actuating member, a spring retainer slidably disposed in the main body and normally abutting the lower end of the actuating member to transmit the biasing force of the spring to the actuating member, a stop provided on the inner surface of the main body for abutting engagement by the spring retainer in the non-actuated condition of the dispenser, a pawl pivotally connected to the spring retainer, a pawl spring for biasing the pawl in the radially outward direction, a rack shaft slidably provided on a side surface of the main body and having a plurality of rack teeth thereon for engaging with said pawl, means for preventing the pawl from engaging with the rack shaft when the spring retainer abuts against the stop, a suction button connected to the rack shaft and slidable along a longitudinal recess in the main body, and a cylinder piston device with the cylinder thereof being connected to the main body and the piston thereof being connected to the lower end of the rack shaft.
The dispenser operates generally satisfactorily, however, it is required in chemical or pharmaceutical tests or analysis to dispense predetermined same quantities of liquid to a plurality of discrete locations simultaneously so as to perform a multiple member of tests efficiently.